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Occupational Safety and Health Branch Labour Department
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Page 1: Fafa

Occupational Safety and Health BranchLabour Department

Page 2: Fafa

LIGHTING IN OFFICES 2

his guide is intended to help employers and

employees assess the health risks associated with

lighting in their workplace. Such assessments

can be no more than an examination of what, in the

course of work, could possibly cause harm to people.

By following this guide, you may identify hazards, the

degree of risk and the possible solutions.

T

LIGHTINGLighting is an essential provision for any workplace. It is preferrable to

provide uniform illumination over the entire workplace by combining both

natural and artificial lighting. Localised lighting may be required in certain

cases to cut costs and improve illumination. Good lighting helps us to see

and to recognise hazards. It can reduce visual strain and discomfort. Poor

lighting may affect workers' performance and health as poor visibility

increases the chances of errors being made. It also means that people work

slower. Besides, natural working posture may not be possible under poor

lighting, thus resulting in musculo-skeletal strain.

Fig. 1. Different Light Provisions

(a) General & Uniform (b) Localised (c) Local

September 2003 Third Edition

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3 LIGHTING IN OFFICES

RISK ASSESSMENTThe following checklist is designed to help you assess the health risks at

your workplace. Answer all the questions and if your answer(s) is the same

as that indicating “potential hazards”, there are deficiencies in the safety

system or there are situations that can cause health hazards/accidents. You

are advised to go through the guidance materials presented in the following

sections and apply suitable solutions to eliminate or reduce the health

hazards. Should you get matched answers in question 2, 3, 4, 5, 6, 7, 8 or

10, you will probably experience visual strain or fatigue and may require

immediate remedial actions.

The checklist may not cover all the situations in your workplace. You are

free to add more or modify the questions to suit your specific needs.

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LIGHTING IN OFFICES 4

1. Is there only natural or general lighting providedin your workplace?

2. Are there sufficient light fittings and are theywell distributed?

3. Are there any glare problems?If yes, what is the glare effect like?(Disability glare or Discomfort glare)

4. Does the lighting make a harsh contrast betweenyour work and its surroundings?(e.g. the desktop and the far corners)

5. Are the contrast and brightness of the tasksatisfactory, when it is compared with theimmediate background? (e.g. the document relativeto the desktop)

6. Are there any shadows cast across your work station?

7. Is the lighting too dim?

8. Is there too much light?

9. Is the lighting colour suitable for your activity?

10. Do any of the lights flicker?

11. Is there any heat radiation or hot spot effectsfrom the lighting?

12. Do you experience visual strain or frequentheadaches?

13. Do you work long hours in front of a computer screen?

14. Do you have access to the lighting controls?

15. Is there a schedule or a plan for maintenance of

the lighting in your workplace?

Answers indicating

potential hazards

Yes

No

Yes

Yes

No

Yes

Yes

Yes

No

Yes

Yes

Yes

Yes

No

No

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5 LIGHTING IN OFFICES

Here are further comments and possible solutions to the problems that you

may have found when you follow the assessment procedure.

1. In modern buildings, artificial lighting is essential for work. There

should be facilities for general lighting, localised lighting or local

lighting to suit different purposes. General lighting is designed for

movement and casual work, such as filing. Localised lighting

provides more intense illumination at the workstations. Local

lighting units illuminate only specific work areas, like a desk.

Natural lighting is often unreliable and it varies with weather

conditions, season and window spacing.

Combine natural lighting with artificial lights to improve

your workplace lighting.

2. General lighting installations are designed to provide uniform

illumination over the whole workplace. Both quality and quantity

of light are important.

Light sources should be well located, illuminating the

workplace as well as entrances and corridors.

A workplace should have a comfortable and uniform

illumination.

PROBLEMS & SOLUTIONS

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LIGHTING IN OFFICES 6

3. If lights are too bright, glare will result and may affect visibility.

Disability glare usually happens when broad-band light

illuminates your workstation, like light from a window.

Reposition your workstation to prevent such light sources falling

within your field of vision. For example, align your workstation at

right angle to windows and similar light sources.

Fig. 2a Disability glare from a light fitting Fig.2b Disability glare from windows

Discomfort glare does not cause direct visual interference, but it

can be annoying or uncomfortable. It can be caused by direct or

reflected light. This can be avoided by

reposition the light source(s) and, or your workstation

appropriately,

avoid the use of well-polished surfaces and

reduce the contrast between your work area and its

surrounding.

Fig. 3 Veiling reflections: thereflection of the lights ismasking information on the screen.

Fig. 4 Distraction reflection closeto the line of sight.

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7 LIGHTING IN OFFICES

The working environment

4. Optimum lighting conditions also depend on an optimum contrast

between illumination of your workstation and its surroundings.

The lighting contrast between your workplace and the

surroundings should be no more than a ratio of 10:1.

(For example: the desktop and the far corners of the room)

A bright light source near the light of sight is distracting,

but this can be reduced by ensuring your workstation is

within the brightest part of the workplace.

5. The light contrast between your task at the workstation and its

immediate background should not exceed a ratio of 10:3. (For

example: the document and the desktop)

The brightness contrast may be reduced by altering the

intensity and direction of the nearby light sources.

The changes between task

illuminance and illuminance of

immediate surroundings should

be gradual to avoid harsh

contrasts.

Individual lamp in dark

environment gives maximum

concentration but prolonged

work under such illumination

will lead to visual fatigue.

Fig. 5 Illumination and contrast

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LIGHTING IN OFFICES 8

6. Backlighting will cast shadows of your head and, or body across

your workstation. To avoid casting shadows, attention should be

paid on the direction of the lighting.

Change the direction of your nearby light sources may avoid

the shadowing effect. It is preferable to have lighting from

the left for right-handed person, and vice versa.

7. There are many causes for insufficient lighting: too little light,

shadows or dirty light sources. Insufficient lighting may cause you

to squint and is likely to cause eye strain. The optimum light intensity

for workplaces depends on the task at hand. Some examples of

optimum illuminance for special activities in an office are given in

the appendix. For details, consult the health and safety personnel.

The minimum level of illumination recommended for work

in general offices is 200 lux.

Local lighting can improve illumination of your workstation.

8. Fine works usually need more light but too much light can cause

eye-strain.

Extra lighting can be avoided by removing lights from your

field of vision or by reducing the light intensity.

The optimum lighting for normal desk work is between 300

and 500 lux. It should not be less than 200 lux under any

condition.

Local lights that are easy to clean and to maintain can be

used for precision work.

9. If you are working with colours, like paint or ink, the type of lamp

you use will be important. Generally lamps with high luminous

efficiency render colours poorly but fluorescent lamps give both

good colour rendering and good vision.

Use daylight bulbs or fluorescent tubes for colour

recognition tasks.

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9 LIGHTING IN OFFICES

Fig. 6 Lighting for inspection purposes

10. Light flicker is annoying and can cause visual fatigue and even

accidents. The most likely causes of flicker in offices are old

fluorescent tubes. It can also result from mechanical origins like

rotating fan blades on the ceiling.

Set up a lamp replacement schedule so that lamps are

replaced before worn-out.

Remove the cause of flicker.

11. All electric lamps emit both light and heat. Tungsten filament lamps

or halogen lamps with reflectors may focus the heat radiation

causing possible discomfort or burns. Arc eyes can result if an

incandescent source gives off ultraviolet radiation too.

Use ‘air-handling’ reflectors that disperse the heat, or

Use uplighters to re-direct the light and heat radiation to

the ceiling.

Alternatively, use higher efficient lamps which demand a

lower wattage, to reduce heat radiation.

Inspection of surface flatnessIrregularities in reflected image

highlight defect on product surfaces.

Inspection of colour‘Light box’ with fluorescent tubes

meeting the requirement of BS 950 allows

colour matching of products.

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LIGHTING IN OFFICES 10

12. The signs and symptoms of visual strain are diverse and complicated,

and come in three forms: ocular, visual and systemic. Ocular

problems should be dealt with by an optician. Visual difficulties

usually result from poor lighting contrast. The most common

systemic symptoms are headache and eye-strain, which are usually

not specific and are therefore overlooked.

The causes should be identified and rectified.

Short and frequent breaks may reduce the complaint.

Regular eye checks are recommended for people needing

glasses.

13. Working on a display screen equipment (DSE) is visually demanding.

If the lighting condition of the workstation is poor, visual strain may

result after long working hours. It may also make the workers to

adopt unsuitable postures that lead to other forms of health concerns

such as neck pain.

General lighting or task lighting should be suitably provided

in accordance with the nature of work and the visual

demand.

For detailed guidelines on working with display screen

equipment, please refer to other revelant publications by

our Department.

Fig.7 Light Distribution Classification

Direct Semi-direct General Indirect semi-indirectDiffusing (up lighters)

Classification

Luminaire

Upper-hemisphere 0-10 10-40 40-60 90-100 60-90

flux

Lower-hemisphere 100-90 90-60 60-40 10-0 40-10

flux

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11 LIGHTING IN OFFICES

14. Flexible or adjustable lighting systems give you better control over

your light sources. In addition, a knowledge of the best lighting

conditions can bring the best of such equipment.

Provide local switch for control of the lighting system.

15. The lighting system should be checked and maintained regularly

(such as cleaning of and replacing bulbs). Ordinary filament bulbs

and fluorescent tubes may last approximately 700 hours and 7,000

hours respectively.

Implement a regular cleaning and maintenance programme

for windows and the lighting system.

Cleaning dirty lamps can improve the efficiency of the lights

by more than 20%.

Appendix

Examples of optimum average illumination in offices

Task position or area Optimum average Notes

illumination in lux

General offices 500

Computer work stations 500 Local lighting may be requiredfor reading a document

Drawing work stations 750 Local lighting is appropriate

Other areas, e.g. file 300storage and reception,

telephone operators

For details, please refer to our ‘Guidelines for Good Occupational Hygiene Practice in a

Workplace’.

Page 12: Fafa

LIGHTING IN OFFICES 12

Other Titles in the Office

Environment Series

1. Introduction and Housekeeping

2. Lighting in Offices

3. Photocopying

4. Ventilation

5. Office Workstation Design

6. Use of Chemicals

7. Manual Handling

THIS GUIDE IS

The Labour Department's contribution towards safety and health - a shared

responsibility - and the Department's endeavour to serve the community.

For further information about the subject or assistance, please contact

Address : Occupational Health Service, Labour Department

15/F, Harbour Building

38 Pier Road, Central

Hong Kong

Tel: 2852 4041

Fax: 2581 2049

Home Page Address: http://www.labour.gov.hk

E-mail Address : [email protected]

FURTHER INFORMATION

Printed by the Government Logistics Department(Printed on paper made from woodpulp derived from renewable forests) 12/2003-3-OHB50


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